A known autostereoscopic display device is illustrated in FIG. 1. This known device 1 comprises a two dimensional liquid crystal display panel 2 having a row and column array of display pixels 3 acting as a spatial light modulator to produce the display. For the sake of clarity, only a small number of display pixels 3 are shown in the Figure. In practice, the display panel 2 might comprise about one thousand rows and several thousand columns of display pixels 3.
The structure of the liquid crystal display panel 2 is entirely conventional. In particular, the panel 2 comprises a pair of spaced transparent glass substrates, between which an aligned twisted nematic or other liquid crystal material is provided.
Each display pixel 3 is associated with a switching element, such as a thin film transistor (TFT) or thin film diode (TFD). The display pixels are operated to produce the display by providing addressing signals to the switching elements, and suitable addressing schemes will be known to those skilled in the art.
The display panel 2 is illuminated by a light source 5 comprising, in this case, a planar backlight extending over the area of the display pixel array. Light from the light source 5 is directed through the display panel 2, with the individual display pixels 3 being driven to modulate the light and produce the display.
The display device 1 also comprises a lenticular sheet 7, arranged over the display side of the display panel 2, which performs a view forming function. The lenticular sheet 7 comprises an array of lenticular elements 9 extending parallel to one another, of which only one is shown with exaggerated dimensions for the sake of clarity.
Thus, an array of elongate lenticular elements 9 extending parallel to one another overlies the display pixel array, and the display pixels 3 are observed through these lenticular elements 9.
The lenticular elements 9 act as a light output directing means to provide different images, or views, from the display panel 2 to the eyes of a user positioned in front of the display device 1. The above described device provides an effective three dimensional display device.
In an arrangement in which, for example, each lenticular element 9 is associated with two columns of display pixels 3, the display pixels 3 in each column provide a vertical slice of a respective two dimensional sub-image. The lenticular sheet 7 directs these two slices and corresponding slices from the display pixel columns associated with the other lenticular elements 9, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image.
However, use of a liquid crystal display panel is generally limited to display devices below a certain size and is not cost-effective for large screen sizes. Thus, for applications which require a large screen size, such as home cinema or public displays, there remains a need to provide a cost-effective 3-dimensional (3D) display solution.
For display applications requiring a large screen size, it is known to use a projection-based display system in which images are projected on to a large flat panel or screen using a projector (positioned either in front of or behind the panel/screen).
It is also known to employ two projectors in order to create a 3D or stereoscopic projection-based display from a stereoscopic pair of images. In such systems, the two projectors each project an image using light having a state of polarization that is orthogonal to that of the other projector. The projection screen is arranged to conserve the state of polarization of the projected light and, by means of polarizing glasses which select one state of polarization for one eye and the other state of polarization for the other eye, the two overlapping images are perceived so that the user observes a single stereoscopic image.
Although this method provides good 3D depth perception, the method relies on the user wearing special glasses, which is undesirable.
Other known 3D projection-based display systems require the use of many projectors, each projector being responsible for one view of a multi-view 3D image. In addition to being highly expensive, these systems have the disadvantage of being unreliable since the light source in each projector (typically a Ultra-High Performance lamp) has a limited lifetime and predicting its end-of-life is practically impossible.